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Applied aspects of domain-acoustic echo in polycrystalline ferrites
,~4 Journal of mnad gnetlsm magnetic ELSEVIER
Journal of Magnetism and Magnetic Materials 196-197 (1999) 607-608
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m•erlais
Applied aspects of domain-acoustic echo in polycrystalline ferrites V.O. Golub a, V.V. Danilov b, A.M. Pohorily a'*, I.V. Z a v i s l y a k b *lnstitute of Magnetism NAS of Ukraine, 36-B Vernadsky str., 252142 Kiev, Ukraine bRadio-Physical Department, Kiev National University, 6 Glushkova str., Kiev, Ukraine
Abstract The possibility of use of the domain-acoustic echo phenomenon for the primary processing of radio signals has been investigated. It has been shown that the domain-acoustic processor allows a simple provision of real-time signal correlation, inversion and extraction from noise. © 1999 Elsevier Science B.V. All rights reserved. Keywords: Domain-acoustic echo; Signal processing; Correlation function; Signal recording
One of the newest phenomena revealed in some polycrystalline ferrites is the memorizing of acoustic signals or the so-called domain-acoustic echo (DAE) [1-3]. The typical scheme for investigation of domain-acoustic echo is the following. A piezoacoustic transformer exciting acoustic waves is fixed on one side of a ferrite rod. A recording/registering coil (6-10 loops) is wound around the rod. The recorded acoustic signal is excited in the rod by means of piezotransformer. A short recording magnetic pulse (radio pulse of the same frequency or 6-like one) is excited in the coil with a propagation delay of the acoustic signal. A space-periodic magnetic structure is formed as a result of nonlinear magnetoacoustic interaction of acoustic and magnetic waves AM(x) = F( - x/v)e-ik~.
(1)
Here x is the coordinate in the direction of propagation of acoustic wave, v is the sound velocity, and k is the wave vector. This structure is an image of an acoustic signal and can be stored for practically unlimited time. It has been shown that the appearance of such a stationary space-periodic magnetic structure can be connected with processes of irreversible change of magnetization [4]. The recorded information can be read exciting the sec-
*Corresponding author. Tel.:/fax: + 380-44-4441020;e-mail: [email protected].
ond acoustic signal in the rod and registering response in the coil. The information can be erased by demagnetizing the rod. DAE phenomenon apparently can be used for the creation of a domain-acoustic processor. Such processors can perform integral transformations such as convolution, correlation, and signal time inversion and also can be used as memory devices and delay lines. This work is devoted to the investigation of some possible applications of the DAE processor. The main experimental results were obtained on a Nio.9sCoo.02Fe20 3 polycrystalline ferrite rod of 90 x 5 × 5 mm 3 size. An LiNbO3 piezotransformer for excitation of transverse acoustic waves of frequency f ~ 10 MHz was situated on one end of the rod. Measured sound velocity was 3.9 x 104 m/s. The following signals were used for the test of the DAE processor: a plain radio pulse of zi = 5 ~ts length and Af = 200 kHz spectrum width; a pair of coherent plain pulses of z~ = 2.5 gs and T2 5 ~S lengths (see Fig. la); a linear frequency modulated (LFM) radio pulse of zi = 28 las length, A f = 6 MHz spectrum width, and B = 169 base (see Fig. 2a). If recorded information (1) is read by means of an acoustic wave the signal =
U(t) ~
F( -- x/v)G(t -- x/v)dx.
0304-8853/99/$ - see front matter © 1999 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 8 8 5 3 ( 9 8 ) 0 0 8 6 1 - 0
(2)
608
KO. Goluh et al. /Joulwal o/Magnetism and MaLmeticMateriaLs' 196-197 (1999) 607 60A'
Fig. 2. Experimentally obtained oscillograms. (a) The recorded LFM signal (upper scanl and correlation function of the pair of LFM signals. (b) Reading acoustic signal which is the additive mix of the LFM signal and white noise in the relation is 1 : 3 (upper scan) and the correlation function of the recorded signal and this one. If the reading signal is a
U(~)-f~F(-.x-/v)6(t-x/,~)dx=l:(
Fig. 1. Experimentally obtained oscillograms. (a} The recorded pair of the plain pulses. (b) The inversion signal read by a ~-like pulse (the pulse distortions are connected with the dumping of acoustic waves in the rod). {c) Correlation function of two pairs of plain pulses.
t),
(4)
i.e. time inversion takes place. The experimental oscillogram for this case is represented in Fig. lb. Use of L F M radio pulses allows the extraction of signals from noise. The example of the extraction is shown in Fig. 2b.The characteristic feature of the DAE processor is its rapid action. The time of signal processing is equal to the signal length (i.e. m i n i m u m possible). This fact allows the use of the D A E processor in real-time systems. This work was partially supported by S T C U project N391.
References forms in the coil. The substitution r = - x/c reduces Eq. (2) to the form U(t) ~ ~i~ F(r)G(t + r) dx.
(3)
So this is a correlator. The examples of this processing of the signals are represented in Fig. lc and Fig. 2a.
[1] M.V. Manuilov, V.S. Bondarenko, V.V. Krinochkin, B.V Sobolev, JETP Lett. 43 (1986) 470. [2] V.S. Bondarenko, A.F. Kabachenkov, G.D. Mansfel'd, M.V. Manuilov, A.A. Rubtsov, V.G. Shavrov, Zh. Tekh. Fiz. 60 (1990) 123 [Tech. Plays. 35 11990)]. [3] V. Ermolov. J. Stor-Pellmen. M. Luukkala, J. Phys. D 30 (1997) 1734. [4] V.O. Golub. V.V. Kotov. A.N. Pogorely, submitted tot publication.
Journal of Magnetism and Magnetic Materials 196-197 (1999) 607-608
,~
m•erlais
Applied aspects of domain-acoustic echo in polycrystalline ferrites V.O. Golub a, V.V. Danilov b, A.M. Pohorily a'*, I.V. Z a v i s l y a k b *lnstitute of Magnetism NAS of Ukraine, 36-B Vernadsky str., 252142 Kiev, Ukraine bRadio-Physical Department, Kiev National University, 6 Glushkova str., Kiev, Ukraine
Abstract The possibility of use of the domain-acoustic echo phenomenon for the primary processing of radio signals has been investigated. It has been shown that the domain-acoustic processor allows a simple provision of real-time signal correlation, inversion and extraction from noise. © 1999 Elsevier Science B.V. All rights reserved. Keywords: Domain-acoustic echo; Signal processing; Correlation function; Signal recording
One of the newest phenomena revealed in some polycrystalline ferrites is the memorizing of acoustic signals or the so-called domain-acoustic echo (DAE) [1-3]. The typical scheme for investigation of domain-acoustic echo is the following. A piezoacoustic transformer exciting acoustic waves is fixed on one side of a ferrite rod. A recording/registering coil (6-10 loops) is wound around the rod. The recorded acoustic signal is excited in the rod by means of piezotransformer. A short recording magnetic pulse (radio pulse of the same frequency or 6-like one) is excited in the coil with a propagation delay of the acoustic signal. A space-periodic magnetic structure is formed as a result of nonlinear magnetoacoustic interaction of acoustic and magnetic waves AM(x) = F( - x/v)e-ik~.
(1)
Here x is the coordinate in the direction of propagation of acoustic wave, v is the sound velocity, and k is the wave vector. This structure is an image of an acoustic signal and can be stored for practically unlimited time. It has been shown that the appearance of such a stationary space-periodic magnetic structure can be connected with processes of irreversible change of magnetization [4]. The recorded information can be read exciting the sec-
*Corresponding author. Tel.:/fax: + 380-44-4441020;e-mail: [email protected].
ond acoustic signal in the rod and registering response in the coil. The information can be erased by demagnetizing the rod. DAE phenomenon apparently can be used for the creation of a domain-acoustic processor. Such processors can perform integral transformations such as convolution, correlation, and signal time inversion and also can be used as memory devices and delay lines. This work is devoted to the investigation of some possible applications of the DAE processor. The main experimental results were obtained on a Nio.9sCoo.02Fe20 3 polycrystalline ferrite rod of 90 x 5 × 5 mm 3 size. An LiNbO3 piezotransformer for excitation of transverse acoustic waves of frequency f ~ 10 MHz was situated on one end of the rod. Measured sound velocity was 3.9 x 104 m/s. The following signals were used for the test of the DAE processor: a plain radio pulse of zi = 5 ~ts length and Af = 200 kHz spectrum width; a pair of coherent plain pulses of z~ = 2.5 gs and T2 5 ~S lengths (see Fig. la); a linear frequency modulated (LFM) radio pulse of zi = 28 las length, A f = 6 MHz spectrum width, and B = 169 base (see Fig. 2a). If recorded information (1) is read by means of an acoustic wave the signal =
U(t) ~
F( -- x/v)G(t -- x/v)dx.
0304-8853/99/$ - see front matter © 1999 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 8 8 5 3 ( 9 8 ) 0 0 8 6 1 - 0
(2)
608
KO. Goluh et al. /Joulwal o/Magnetism and MaLmeticMateriaLs' 196-197 (1999) 607 60A'
Fig. 2. Experimentally obtained oscillograms. (a) The recorded LFM signal (upper scanl and correlation function of the pair of LFM signals. (b) Reading acoustic signal which is the additive mix of the LFM signal and white noise in the relation is 1 : 3 (upper scan) and the correlation function of the recorded signal and this one. If the reading signal is a
U(~)-f~F(-.x-/v)6(t-x/,~)dx=l:(
Fig. 1. Experimentally obtained oscillograms. (a} The recorded pair of the plain pulses. (b) The inversion signal read by a ~-like pulse (the pulse distortions are connected with the dumping of acoustic waves in the rod). {c) Correlation function of two pairs of plain pulses.
t),
(4)
i.e. time inversion takes place. The experimental oscillogram for this case is represented in Fig. lb. Use of L F M radio pulses allows the extraction of signals from noise. The example of the extraction is shown in Fig. 2b.The characteristic feature of the DAE processor is its rapid action. The time of signal processing is equal to the signal length (i.e. m i n i m u m possible). This fact allows the use of the D A E processor in real-time systems. This work was partially supported by S T C U project N391.
References forms in the coil. The substitution r = - x/c reduces Eq. (2) to the form U(t) ~ ~i~ F(r)G(t + r) dx.
(3)
So this is a correlator. The examples of this processing of the signals are represented in Fig. lc and Fig. 2a.
[1] M.V. Manuilov, V.S. Bondarenko, V.V. Krinochkin, B.V Sobolev, JETP Lett. 43 (1986) 470. [2] V.S. Bondarenko, A.F. Kabachenkov, G.D. Mansfel'd, M.V. Manuilov, A.A. Rubtsov, V.G. Shavrov, Zh. Tekh. Fiz. 60 (1990) 123 [Tech. Plays. 35 11990)]. [3] V. Ermolov. J. Stor-Pellmen. M. Luukkala, J. Phys. D 30 (1997) 1734. [4] V.O. Golub. V.V. Kotov. A.N. Pogorely, submitted tot publication.